Doubt in Recursion-All Subsequences

#1

The code is running fine for the given input ab but while submitting on hacker blocks, the test case is not being passed.
Question
RECURSION - ALL SUBSEQUENCES
Print all the subsequences of a string in lexicographical order.

Input Format:
First line contains an integer N, the no of strings.
Next, N lines follows one string per line.

Constraints:
1 < len(str) < 20

Output Format:
No of subsequences one per line

Sample Input:
1
ab
Sample Output:

a
ab
b
Explanation:
4 subsequences are printed.
Empty string is a subsequence.
Code https://ide.codingblocks.com/s/116064

#2

In your code empty string is Printed at end
while question say it should print in first line
just make that change
all testcases willl passed

#3

Now I’ve placed the null set first, but still the test case is not being passed.
Here is the code